A typical washing machine for washing clothing goes through a wash cycle which includes a number of modes of operation. Generally, the wash cycle includes an agitation mode in which the clothes are agitated in detergent, a rinse mode, and a spin mode in which water is removed from the clothes.
Washing machines generally include two components which come into contact with the clothes, the basket and the agitator. The basket is typically a cylindrical container which holds the clothes to be washed and which may have holes in its walls to drain the washing liquid (e.g., detergent and water) during the spin cycle. The agitator is located within the basket and serves to agitate the clothes and the wash liquid in the basket. The combination of the mechanical action of the agitator and the chemical action of the wash liquid washes the clothes. The basket and agitator are generally located within a second container conventionally known as the tub. The tub keeps the wash liquid within the basket during the wash cycle.
To power the agitator and the basket, a conventional induction motor may be used. The basket and agitator each have drive shafts, which may be concentric, for independently driving their respective motions. The agitator drive shaft may be connected to the motor through a transmission. The transmission reduces motor speed and converts the rotary motion of the motor into an oscillatory output for the agitator drive shaft. The basket drive shaft is typically connected to the motor through the outer case of the transmission.
During the agitation mode, the basket drive shaft is held stationary while the agitator drive shaft is oscillated. The basket drive shaft is typically locked to the washer frame through a brake and carries the reaction forces from the transmission during agitation into the frame. During the spin mode, power is applied to the basket drive shaft, and both the agitator and basket drive shafts are rotated together. During spin mode, the brake is released so the basket and agitator can be spun up to a high speed to expel wash water from the clothes through holes in the basket.
To switch from agitation mode to spin mode, a mode shifter is used. The mode shifter changes the point of power application from the agitator to the basket. An automatic brake is also provided to quickly stop the basket to avoid an accident if the washer lid is raised during the spin mode. There are many known ways of achieving the mode shift and brake functions. A common problem with many systems is the level of mechanical complexity of each, which adversely effects cost and reliability. There is a need for mode shifters which are more mechanically simple and inexpensive. Such systems need to overcome the problems encountered in known systems while at the same time not creating new problems such as safety concerns which would result if the washer fails to shut down when the washer lid is opened during operation.